This invention relates to a cylindrical member having an outer surface coating of substantially uniform radial thickness. More particularly this invention relates to a roto-gravure printing cylinder whose outer surface is formed by an epoxy.
From Pfleger et al. U.S. Pat. No. 4,007,680, which issued Feb. 15, 1977, and of which the present applicant is one of two joint inventors, it is known to provide a roto-gravure printing cylinder having an inner cylindrical member of alumnium or steel or phenolic material and an epoxy coating on the outer surface of the inner cylindrical member. The Pfleger et al. patent discloses applying an uncured mixture of epoxy resin and hardener to the outer surface of the inner clindrical member by reciprocating a brush longitudinally of the inner cylindrical member while the latter is rotated about its axis, thus to spread the uncured mixture to a desired radial thickness or depth as determined by forming members at opposite ends of the cylindrical member. When the level of the uncured mixture becomes flush with the peripheries of the forming members, application of the mixture is stopped and rotation of the coated member is continued for an additional four hours, or until the mixture sets or cures.
As is taught by the Pfleger et al. patent, the cured epoxy coating adheres very well to steel, aluminum and phenolic surfaces. The Pfleger et al. patent further teaches that the cured coating of the completed roto-gravure printing cylinder need not be provided with the required printing images by the use of acids, but can be easily engraved electronically to provide clearly defined printing images which will maintain good clarity of form through prolonged printing operations.
However, the manner of producing the printing cylinder disclosed in the Pfleger et al. patent is cumbersome and slow and is subject to inaccuracies in the thickness of the coating as well as being subject to deviations of the outer surface of the coatings from the required cylindrical shape. Further and most important, the surface of the coatings are subject to porosity.
An important object of the present invention is to provide an improved method and apparatus which overcomes the aforementioned disadvantages of the prior art, by providing a relatively rapid and sure method and apparatus for producing accurate, high quality non-porous roto-gravure printing cylinders or other cylindrical articles.